By now, everyone knows that second-hand smoke is dangerous to humans. But in recent years, numerous studies have proven that it’s also very dangerous to our pets.

Second-hand smoke, also known as environmental tobacco smoke, comes from two sources: smoke that is exhaled by the smoker, and the smoke produced at the end of a burning cigarette, cigar, or pipe. According to the American Lung Association, second-hand smoke contains over 7,000 chemicals, including tar, carbon monoxide, arsenic, ammonia, nicotine, and formaldehyde. Over 70 of these chemicals are known to cause cancer.

Second-hand smoke has been linked to respiratory diseases, allergies, and cancer in dogs and cats, and has been shown to cause eye and skin diseases, cancer, and respiratory problems in birds. Smaller pets such as rabbits, rats, mice, and guinea pigs who live in smoking households are particularly affected by second-hand smoke, often suffering from lung cancer, pneumonia, and heart problems.

Why Are Pets So Susceptible To Second-Hand Smoke?

As of 2015, almost 80 million homes in the United States include at least one pet. Unfortunately, recent statistics show that nearly 30% of pet owners live with at least one smoker. And since our pets spend so much more time at home than we do, they are at an even greater risk of exposure to harmful chemicals in homes where people smoke.

Specifically, here’s what second-hand smoke does to our pets.

Cats

Cats are particularly susceptible to second-hand smoke because they spend so much of their time grooming. Once carcinogens in cigarette smoke settle out of the air, they stick to everything – clothing, carpeting, draperies, and unfortunately, our pets’ fur. Cats then ingest these particles while grooming themselves, which directly exposes the mucous membranes in their mouths to these cancer-causing agents. This makes cats more prone than any other pet to developing oral cancer from second-hand smoke.

Cats groom not only themselves, but each other, leading to increased exposure to harmful smoke particles.

According to a study published in the American Journal of Epidemiology, cats living in homes with smokers are 3 times more likely to develop malignant lymphoma than cats living in nonsmoking households. And a study published in Veterinary Medicine Magazine in 2007 also found that cats exposed to smoke from even just one cigarette per day are 4 times more likely to be diagnosed with oral squamous cell carcinoma, an extremely aggressive type of mouth cancer. Over 90% of cats diagnosed with oral squamous cell carcinoma die within a year, even with chemotherapy and radiation treatment.

Cats who are exposed to cigarette smoke can also suffer from asthma, eye irritation, wheezing, coughing, lethargy, and depression. A University of Minnesota study in 2007 showed that cats who live with smokers actually have nicotine and other cigarette toxins present in their urine.

Dogs

Because they tend to go outside more frequently and are bathed more often, dogs get somewhat more of a break from second-hand smoke in comparison to cats. However, dogs are equally susceptible to the dangers of second-hand smoke.

The American Journal of Epidemiology reported that dogs in smoking households have a 60% greater risk of developing lung cancer than dogs in nonsmoking households. Many dogs also experience allergic reactions from cigarette smoke, causing them to chew, scratch, and bite at their skin and fur.

A recent study by Colorado State University showed that longer-nosed breeds of dogs who live in smoking households are particularly susceptible to developing cancerous nasal and sinus tumors. Since these dogs have more surface area in their noses, there’s more space for inhaled smoke particles to accumulate and become trapped. Dogs who suffer from nasal cancer usually will not survive more than one year after diagnosis.

On the other hand, short-nosed breeds of dogs (such as Bulldogs and Pugs) have higher rates of lung cancer, since inhaled smoke particles have less of a chance to become trapped in their nasal passages, and instead go directly to their lungs.

Birds

Birds suffer greatly from exposure to second-hand smoke, as their respiratory systems are extremely sensitive to any type of airborne particles or pollutants. Birds who are exposed to even small amounts of second-hand smoke can quickly develop pneumonia, as well as lung cancer, eye problems, skin irritation, heart issues, coughing and wheezing, and fertility problems.

Birds who sit on the hand of a smoker can develop severe reactions to the nicotine residue on the person’s hand. This can result in contact dermatitis, and cause the bird to begin pulling out its own feathers.

The Next Generation: Third-Hand Smoke

As if second-hand smoke wasn’t bad enough, a Harvard Medical School study published in 2009 in the Journal of Pediatrics identified what they called “third-hand smoke”. This is the invisible, yet highly toxic, mixture of gases and particles that cling to smokers’ clothing, hair, furniture, carpeting, and car interiors long after the second-hand smoke has cleared.

Smoking outdoors will still not protect your pet from the dangers of second-hand smoke.

Third-hand smoke is what can be smelled in a home, car, or hotel room, even after it has been thoroughly cleaned. It’s thought to react with other indoor pollutants to create an even more toxic mix, and it can’t be eliminated just by opening a window or turning on a fan. Although third-hand smoke is still being studied, researchers believe that children, pets, and nonsmoking adults are all at risk when they ingest or touch substances contaminated with third-hand smoke.

Preliminary third-hand smoke studies indicate that even pets who live in a home where there are designated smoking areas (such as outside patios or certain rooms in the house) are not safe from the chemical residue of cigarette smoke. The only way to eliminate the risk is to create a completely smoke-free environment.

What Can You Do To Protect Your Pets From Second-Hand Smoke?

The most obvious answer to this question is certainly not the easiest one, but here it is: if you are a smoker, quit smoking. You owe it to yourself, your pets, and your family and friends to eliminate the danger of second-hand (and third-hand) smoke exposure.

In the meantime, while you’re going through the quitting process, there are some things you can do to somewhat reduce the risk to your pets.

Take it outside. Although smoking outdoors won’t completely eliminate the danger to your pets from cancer-causing particles, it will prevent a portion of these particles from settling on their fur. And never smoke with your pets in the car, even with windows down – the confined space just makes the smoke that much more concentrated.

Use a high-quality air purifier with a HEPA filter inside your home to remove excess particles and toxins. Avoid anything labeled “ionic air cleaner” or “ionizing filter”, as these are not as effective as HEPA air purifiers, and the ozone produced by these devices can cause breathing problems for both people and pets.

Wash your hands after smoking and before you touch your pets.

Change your clothes after smoking, and try to wash your clothing as quickly as possible. If you can’t wash it immediately, place it in a bag and put it outside until you can.

Speak with your veterinarian, who may be able to recommend an antioxidant health supplement for your pets to help reduce the impact of the toxins on their bodies. Also consider bringing your pets in for a check-up every 4 to 6 months instead of once per year – this is especially important for early detection of mouth cancer in cats.

If you are a nonsmoker, remember that a growing body of evidence shows that there are no “safe” levels of exposure to second-hand smoke – for humans or for pets. Therefore, it’s best to keep your pet away from any situation where someone is smoking.

Smoking Pet Parents: You Can Kick This Thing

The good news is that many pet parents who smoke are becoming more aware of the dangers of second-hand smoke, and are starting to become more motivated to quit. A study published in 2009 in the Tobacco Control Journal found that 28.4% of smokers who participated in an online survey said that learning the facts about second-hand smoke and what it does to their pets would motivate them to quit for good, and 8.7% would ask the people with whom they live to stop smoking.

Second-hand smoke contaminates homes, cars, clothing, skin, and everything else it comes into contact with – and it sticks around for a very long time. If you are currently a smoker, remember that simply smoking outside, or when your pets are not in your house or car, will not protect them. The best way to protect your pets from the cancer and diseases caused by second-hand smoke is to give them a completely smoke-free environment.

Quitting smoking is not easy, no question about it. But if you won’t quit for yourself, will you do it for your pets?

For more information on quitting smoking, check out the following resources:

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I'm an author, founder of the Good Pet Parent Blog, and former Registered Veterinary Technician. Through GoodPetParent.com, I share information on pet health, veterinary terminology, animal behavior and communication, training, and nutrition to help pet parents better understand and care for their animal companions. [More.]